Communication systems for receiving alphanumeric input from a keyboard device and transmitting the received text to a portable receiver such as a selective call receiver are well-known in the art. A drawback to such systems is that a suitable keyboard device may not always be conveniently available to a person desiring to send a text message. One way around this drawback is to provide one or more facsimile inputs for the communication system, the facsimile inputs being compatible with a standard protocol used for communications between facsimile machines. Then, the person desiring to send the text message may print the message on a sheet of paper and send it from a facsimile machine to the communication system.
Because the message comprises scanned text characters, to save transmission time the communication system typically uses conventional optical character recognition (OCR) techniques to convert the characters into character codes, e.g., ASCII codes. The use of OCR causes a new problem, because OCR may not be able to recognize 100% of the human-readable characters in a message. This is particularly true when the message comprises hand printed or handwritten characters.
Conventional OCR systems use various algorithms to determine a confidence level for the recognition of each character. When the confidence level is below a pre-determined level, conventional OCR systems substitute a special character, e.g., "?" for the unrecognizable character. If a message contains too many such unrecognizable character substitutions, the message may become indecipherable when it arrives at the portable receiver. This can occur even for a message that would have been human readable if received as a facsimile and printed on a sheet of paper by a facsimile machine.
Thus, what is needed is a better method and apparatus for encoding, transmitting, and receiving text messages sent from facsimile machines and accepted by facsimile inputs in a communication system.